As well as being a singer-songwriter with folk band the Sussex Wit, Johnny Flynn has had a number of acting roles in theatre, TV and film, including Clouds of Sils Maria. Michael Pearce’s film Beast, in cinemas from 27 April, is about the relationship between Moll (Jessie Buckley) and Pascal (Flynn), an outsider who is considered a suspect in a string of violent crimes.

This is quite a hard film to describe without spoilers, so I’ll let you do it...I think a good way of framing it is as an adult fairytale, in which dark, subconscious forces in these repressed characters collide with the surface of the real world. This is what happens in a lot of traditional fairytales – they’re a way of understanding our darker nature. The name of the film is quite apt, because you don’t know who or what the beast is, and it asks that question once you start watching.

Did you and Michael Pearce make a decision on whether your character was guilty or not?We played around with it: when we were filming we might emphasise it one way, then do another take where it was more ambiguous. You can watch the film and have a feeling about it one way, then reflect and actually think it was totally different. I’ve seen it once and it felt like a different film to the one I had in my head when we were doing it – in a really good way.

How did you manage to find the right balance between charming and dangerous?The thing about Pascal is he believes in himself: he’s fought against the system all his life and has hit an equilibrium where he’s established a life for himself. I had a lot of sympathy for him – it’s important when you’re playing a character to believe in your own validity. I wanted him to have the same sense of release in meeting Moll that she has in meeting him. You have to believe they have something special and could potentially save each other somehow.

What do you think attracts Jessie Buckley’s character to someone who is potentially dangerous?Michael grew up in Jersey and he showed us a side of it that has this small-island mentality – conservative, stuffy, suburban – and Moll is from that environment. Pascal represents a sense of freedom, and when we meet her she’s desperate to get out – even though it seems quite dangerous, it’s thrilling. He’s the only person who really sees her and treats her with respect, without her having to apologise all the time for something she did in her past.

Can making audiences uncomfortable be a healthy thing?Definitely. I think we’re waking up, as a race, to uncomfortable truths about ourselves. We’ve been kind of rolling along in this bubble, needing soporific entertainment to ease us along, and suddenly we’ve woken up to all these things that have exploded in ourselves: realisations about the lack of equality between men and women, or the way we’ve dealt with difficult decisions in the last two years. We all have these shades in our nature: it’s a spectrum within all of us. So I think that’s a clever form of storytelling at the moment, where you’ve been lulled into a sense of agreeing with something, because we need to have those sides of ourselves questioned.

If you’re playing quite a dark role, is it difficult getting out of character at the end of the day?I’ve just come back from doing Hangmen, a Martin McDonagh play in New York, and that character is definitely some sort of psychopath. Our job as actors is to invent the things that bridge ourselves with the characters, so you have to build something if it’s not there – you try and learn what makes people behave in a certain way. It’s interesting coming back to neutral and remembering who you are and what your moral standing point is in the world. But I find I miss characters as I leave them behind.

Were you glad when your Channel 4 show Scrotal Recall was renamed Lovesick after moving to Netflix?I think I was the only one who was weirdly attached to the name. I like really bad puns – proper, red-top, nasty puns – I find them funny. But it did make it easier to tell the headmistress of my son’s nursery what I was doing. Netflix did all these polls in America, and even the people who liked the show wouldn’t tell anyone about it because they didn’t want to have to say the word “scrotal”.

On Twitter you describe yourself as a musician/actor/gardener. How’s your garden coming along?I was in New York until about two weeks ago, and I’ve come straight down to Wales with the family, so I haven’t really been to the garden in London this year. But I’d stolen a load of wild garlic from a walk somewhere, and I was really excited to see that’s starting to come up, as well as all these tulip and daffodil bulbs I’d put in the ground about two years ago. They were given to me by a cousin who died last year, so it’s lovely that they’ve come back.